Saturday, October 22, 2011

German ROSAT Space Junk Satellite Re-Entered Earth's Atmosphere

As previously reported by last month, Germany's ROSAT space junk satellite had been predicted to fall to earth in early November by DLR, Germany's scientific research agency.

DLR has issued a statement that ROSAT re-entered the Earth's atmosphere sometime between 9:45 PM EDT Saturday (03:45 CEST Sunday) October 22 and 10:15 PM EDT Saturday (04:15 CEST Sunday) October 23, 2011.

Based on this timeline, places the re-entry point somewhere between northeastern China and the Pacific Ocean.

When the spacecraft (which was launched from Cape Canaveral Air Forces Station in 1990) re-enters the atmosphere at a speed of approximately 17,000 miles per hour, the X-ray observatory will break up into fragments, some of which will burn up by the extreme heat. 

The latest studies reveal that it is possible that up to 30 individual pieces weighing a total of 1.7 tons may reach the surface of the Earth. 

The largest single fragment will probably be the telescope's mirror, which is very heat resistant and may weigh up to 1.7 tons.

The time and location of re-entry cannot be predicted precisely.

Currently, the re-entry date can only be calculated to within plus/minus one day. 

This time slot of uncertainty will be reduced as the date of re-entry approaches. 

However, even one day before re-entry, the estimate will only be accurate to within plus/minus five hours .

Like UARS, all areas under the orbit of ROSAT, which extends to 53 degrees northern and southern latitude could be affected by its re-entry.  

The bulk of the debris will impact near the ground track of the satellite.  However, isolated fragments could fall to Earth in a 50 mile wide path along the track.

The primary causes of uncertainty in the estimation of a date of the  re-entry date are the fluctuations in solar activity.  Solar radiation heats up the Earth’s atmosphere and therefore increases the atmospheric drag.  Short-term fluctuations in solar activity are governed by an 11 year activity cycle.  At present, we are approaching the next maximum, which has turned out to be much lower than expected.

During the re-entry phase of the satellite, German scientists will be evaluating data from the US Space Surveillance Network (SSN). 

In addition, the Tracking and Imaging Radar (TIRA), the large radar facility at the Fraunhofer Institute for High-Frequency Physics and Radar Techniques in Wachtberg near Bonn will be monitoring the descent of the X-ray satellite to further improve calculations of its trajectory. 

Experts will be analysing the data obtained on behalf of the German Aerospace Center (DLR) to predict the moment of re-entry as accurately as possible.


Space Junk Satellite To Crash On Earth This Weekend